To solve the problem that a magnetron vacuum gage needs a long time until discharge is performed again when discharge stops once, can not measure in a low vacuum region, has a risk breaking a positive electrode in measurement by constant current, and can not perform measurement as it is since abnormal large current is suppressed to be non-linear even when simply flowing the constant current.

The magnetron vacuum gage gives thermal energy to shorten an adsorption desorption time and shortens a discharge start time by increasing motion energy of electrons, in addition, measures both end voltages, a frequency and amplitude of the magnetron vacuum gage by switching over a plurality of the constant currents to compare measured value data by each constant current so as to display a degree of vacuum.